Effects of Constitutive and Inducible Traits of Hybrid Poplars on Forest Tent Caterpillar Feeding and Population Ecology

Abstract

Abstract Hybrid Populus spp. clones, differentially affected forest tent caterpillar, Malacosoma disstria, behavior, development, and population dynamics. Increased larval cohort size and larval silk generally enhanced development. Larval behavior affected developmental success. Under choice conditions, larvae selected more suitable clones, and their growth was enhanced when they moved from less to more suitable hosts. Herbivory by the forest tent caterpillar caused significant reductions in the quality of foliage for subsequent larval development. Polar and nonpolar foliar extracts varied between constitutive and previously damaged plants, and elicited significant larval behavioral responses. The extent to which prior feeding induced foliar changes that affected larval feeding and development varied among clones. The ability of forest tent caterpillar to exploit clones includes genetic and environmental components affecting foliar quality, and includes positive and negative density dependent feedback. In whole-tree field cages, forest tent caterpillar populations increased 9.7x during a 2 yr period on a highly suitable clone, and declined 2.7x on a poor quality clone. The relationships between clonal suitability and forest tent caterpillar population growth were strongly influenced by bud phenology and exudates, in addition to foliar traits. For. Sci. 43(2):252-267.